Most of what a devops person does is in fact development but it is of the non value adding variety. Basically a devops person spends the vast majority of their time configuring common off the shelf software, scripting this or that, etc.
A singular matrix is a matrix which has no inverse because its determinant is zero. If you recall, the inverse of a matrix is. 1/ ad-bc multiplied by: [ d -b ] [-c a ] If ad-bc = 0, then the inverse matrix would not exist because 1/0 is undefined, and hence it would be a singular matrix. E.g.
To Stata, a. matrix is a named entity containing an r c (0 < r  matsize, 0 < c  matsize) rectangular. array of double-precision numbers (including missing values) that is bordered by a row and a column. of names. 1. 2[U] 14 Matrix expressions.